In recent years, an increasing number of electronic devices fed from the municipal electricity supply and/or various DC sources are used in households, hospitals, military, industry, etc. State of the art power supplies employ a circuit comprising a passive input filter, a DDC or a PFC stage and additional circuits according to a particular application. Switchers are designed to operate in buck, buck-boost or boost modes depending on the instantaneous input voltage (Vin) and output voltage (Vo) of the circuit. Consequently, unnecessary losses and harmonic distortions are developed in the circuit, specifically, but not exclusively, during transitions between modes and during buck-boost mode.